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Why is molten slag removed after the ferroniobium reaction?
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niobium processing
Four one-millimetre thick samples of niobium metal foil.
In the aluminothermic process used to produce ferroniobium, molten slag is removed after the reaction because it contains most of the gangue impurities from the concentrate, including all the thorium and uranium oxides. Once the reaction is complete and the slag is tapped off, the vessel can be lifted to allow the remaining metal to solidify.1